// 第一个参数是绑定的this，默认为window，第二个参数是数组或类数组
Function.prototype.apply = function(context = window, args) {
    if (typeof this !== 'function') {
      throw new TypeError('Type Error');
    }
    const fn = Symbol('fn');
    context[fn] = this;
  
    const res = context[fn](...args);
    delete context[fn];
    return res;
  }
  